A 176 KB PDF bearing only the JIS transistor number 2SC3421, categorised as a schematic but most likely a datasheet. The 2SC prefix denotes an NPN bipolar transistor. Such a document is used to confirm lead identification before testing or replacement, to look up maximum collector voltage and current, and to compare the package outline against the board footprint. Open it in a standard PDF reader and check that the code stamped on the component, often C3421, matches.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.